If you do have a "Yellow icon" then you have a basic Layer 1 problem with cabling,speed or duplex setting- make sure your NIC card is enabled and resident in computer configuration - just in case it got disabled or removed by other s/w or service packs/updates etc.
Also manually try changing the speed and duplex of your NIC on your PC, as it could be an autonegotiation issue with your NIC which is causing the problem. Step through the following scenarios and see if link is restored - working from the lowest common denominator
10 M - Half Duplex
10M Full Duplex
100M Half Duplex
100M Full Duplex
You should hopefully find a combination that works.....i.e the Yellow Icon goes away - only then can you start to look at Layer 2(MAC) & 3 for IP addresses.